This is Steven Salzberg's blog on genomics, pseudoscience, medical breakthroughs, higher education, and other topics, including skepticism about unscientific medical practices. Here's where I can say what I really think about abuses and distortions of science, wherever I see them.

Should we all be on statins?

But a new review published earlier this month in the Cochrane Reviews looked at 14 different trials, with a total of 34,272 patients, in an attempt to answer this question, and came out with conflicting results. Scientific and medical experts looked at the review and have already reached diametrically opposed conclusions, reported in their blogs and in commentaries in several leading journals.

Everyone has heard of statins: they are a class of cholesterol-lowering drugs that offer clear benefits in people who already have suffered heart attacks or other serious cardiovascular problems. But what about the rest of us? If you have slightly elevated cholesterol, or even normal cholesterol, should you take statins? Drug companies would certainly like you too, and they have been pushing statins (such as Levacor, Zocor, Pravachol, Lipitor, and Crestor) for years in the U.S., through ad campaigns in print and on television. I wrote about a study of Crestor back in 2008, and I found serious problems with the study's design and conclusions.

First, what did this large-scale review find? All of the studies ran for at least a year, and all were randomized controlled trials, the most rigorous type of study. Overall risk of death was reduced by 17%, and the risk of a heart attack was reduced by 28%, which seem to be very positive results. None of the patients had previous history of cardiovascular disease, although most of the studies recruited patients with other risk factors such as high cholesterol, diabetes, or high blood pressure.

But - and this is a big but - the authors of the Cochrane review had big problems with the way these studies were run. They wrote in their conclusion that

"there was evidence of selective reporting of outcomes, failure to report adverse events and inclusion of people with cardiovascular disease. Only limited evidence showed that primary prevention with statins may be cost effective and improve patient quality of life. Caution should be taken in prescribing statins for primary prevention among people at low cardiovascular risk."

So the review authors were not convinced that people without previous heart disease should all go on statins, even though their own numbers showed a decreased risk. I think their skepticism is justified, because the benefits they observed were very small. This means that subtle biases such as including people who did have cardiovascular disease, could create the appearance of a benefit even if there wasn't one. And 9 of the 14 studies were funded by pharmaceutical companies, which hints at possible bias.

Writing in the journal BMJ, Susan Mayor highlighted the skeptical interpretation. She quoted one of the study's authors, Shah Ibrahim, who said "Absolute benefits were small, and evidence of selective reporting of outcomes makes the evidence less robust.”

"there is solid evidence that statins have a real benefit for primary prevention. This benefit is small, which is exactly what I would predict for a preventive measure in a low-risk population. The data also show that statins are safe. ... For interventions that prevent death – that lower mortality – I think even small benefits are worthwhile."

However, he goes on to say that "it is still unclear where to draw the line in terms of which patients should receive statins."

I would love to believe that statins will reduce everyone's risk of heart disease, but I couldn't ignore one statistic: the "number needed to treat." Based on the new study's findings, you'd have to treat 1000 low-risk patients for one year to prevent one death. To put that another way, if you are at low risk of heart disease, then there is a 99.9% probability that taking statins for a year will give you no benefit. Even so, given that statins have minimal side effects, you might think it's a reasonable preventative treatment, even with such a small benefit. The skeptic in me says that if there was even a tiny amount of bias in some of the trials, that apparent benefit might actually be zero.

On this question, we need more data from completely unbiased studies. In an editorial for the Cochrane Reviews, Carl Heneghan wrote that "Interventions targeting CVD risk reduction in low-risk population should be undertaken in the context of a randomised controlled trial; preventing scarce healthcare resources going to waste."

He's right. Statins might have a small benefit, but before we start prescribing them to tens of millions of people - and before I start taking them myself - I'd like to see unbiased studies conducted exclusively in low-risk populations.